Studies ON SOME NITROGEN Hetrocycles

Abstract

Quinazoline -2,4( I H,3H )-diones were silylated with I, I,I ,3,3,3- hexamethyldisilazane ( HMDS ) in the presence of ammonium sulphate and condensed with methyl 3-azido--5-0-tert-butydliphenylsilyl-2,3-dideoxy-D­ erythro-penyofuranoside 339, which was prepared from 2-deoxy-D-ribose 332 by consecutive methyl glycosidation, S-OH protection with tert­ butylchlorodiphenylsilane, replacement of 3-0H with iodine which in tum replaced by azido goup using , trimethylsilyl trifluoromethanesulfonate ( TMS triflate ) as the catalyst to afford 1-( 3-azido-5-0-tert-butyldiphenylsilyl-2,3- dideoxy-a,p-D-erythro-pentofuranosyl) quinazoline-2,4( 1H,3H )-diones 340 which on treatment with tetrabutylammonium fluoride in THF gave 1-(3-azido- 2,3-dideoxy-a -0-erythro-pentofuranosyl) quinazoline-2,4(1H,3H)-diones 341 and their corresponding p -anomers 50 .

Thieno [2,3-d)pyrimidine-2,4(1H,3H)-dione 56 was silylated with HMDS

and condensed with 339 in acetonitrile in the presence of TMS triflate to yield 1-(3-azido-5-0-tert-butyldiphenylsilyl-2,3-dideoxy- a,P -D-erythro · - pentofuranosyl) thieno [2,3-d)pyrimidine-2,4(1H,3H)-dione 342. Deprotection of 342 was achieved by treatment with Bu4NF I THF to produce 1-( 3-azido-

2,3-dideoxy-a-D-erythro-pentofuranosyl)thieno [2,3-d)pyrimidine-2,4(1H,3H)-